Laptops and notebooks are names for portable computers that have a flat screen and usually weigh less than eight pounds. Most portable computers have connectors for an external monitor and keyboard for transforming them into desktop computers.
FIG. 1 is a block diagram illustrating current display technology found in portable computers. Like most computer systems, a portable computer 10 includes internal hardware and software 12 for operating the system, and a display controller 14 for outputting an internal video signal 16 to a flat panel display 18. The portable computer 10 also includes a digital-to-analog converter 20 and an external CRT connector 22 for outputting the video signal 16 to an external monitor, such as a cathode ray tube (CRT) (not shown). With this type of display architecture, the portable computer 10 is capable of outputting its video signal on the flat-panel display 18, on the external CRT, or on both the flat-panel display 18 and the external CRT at the same time.
The flat-panel display 18 tends to be one of the most expensive components of the portable computer 10. Yet, today many portables 10 become obsolete because various components, such as the processor, deliver lackluster performance relative to new computer systems. Therefore, it would be desirable to continue using the flat-panel display 18 even after that portable computer 10 has become obsolete, perhaps as the monitor of a desktop PC (assuming the desktop PC has a dual display adapter card). The problem is that today's portable computers 10 can only output video signals, but cannot receive video signals from an external source for display on the flat-panel 18.
Accordingly, what is needed is a display controller architecture for portable computers that allows portable computers to display external video signals. The present invention addresses such a need.